Florencio C. Ballesteros

Removal of emerging contaminants by simultaneous application of membrane ultrafiltration, activated carbon adsorption, and ultrasound irradiation.

Advanced wastewater treatment is necessary to effectively remove emerging contaminants (ECs) with chronic toxicity, endocrine disrupting effects, and the capability to induce the proliferation of highly resistant microbial strains in the environment from before wastewater disposal or reuse. This paper investigates the efficiency of a novel hybrid process that applies membrane ultrafiltration, activated carbon adsorption, and ultrasound irradiation simultaneously to remove ECs. Diclofenac, carbamazepine, and amoxicillin are chosen for this investigation because of their assessed significant environmental risks. Removal mechanisms and enhancement effects are analysed in single and combined processes. The influence of adsorbent dose and ultrasonic frequency to EC removal are also investigated. Results suggest that adsorption is probably the main removal mechanism and is affected by the nature of ECs and the presence of other components in the mixture. Almost complete removals are achieved in the hybrid process for all ECs.

Combination of Electrochemical Processes with Membrane Bioreactors for Wastewater Treatment and Fouling Control: A Review

This paper provides a critical review about the integration of electrochemical processes into membrane bioreactors (MBR) in order to understand the influence of these processes on wastewater treatment performance and membrane fouling control. The integration can be realized either in an internal or an external configuration. Electrically enhanced membrane bioreactors or electro membrane bioreactors (eMBRs) combine biodegradation, electrochemical and membrane filtration processes into one system providing higher effluent quality as compared to conventional MBRs and activated sludge plants. Furthermore, electrochemical processes, such as electrocoagulation, electrophoresis and electroosmosis, help to mitigate deposition of foulants into the membrane and enhance sludge dewaterability by controlling the morphological properties and mobility of the colloidal particles and bulk liquid. Intermittent application of minute electric field has proven to reduce energy consumption and operational cost as well as minimize the negative effect of direct current field on microbial activity which are some of the main concerns in eMBR technology. The present review discusses important design considerations of eMBR, its advantages as well as its applications to different types of wastewater. It also presents several challenges that need to be addressed for future development of this hybrid technology which include treatment of high strength industrial wastewater and removal of emerging contaminants, optimization study, cost benefit analysis and the possible combination with microbial electrolysis cell for biohydrogen production.

Incorporation of graphene oxide into a chitosan–poly(acrylic acid) porous polymer nanocomposite for enhanced lead adsorption

The present study describes the successful incorporation of graphene oxide (GO) into a binary polymer composite blend of chitosan–poly(acrylic acid) (CS–PAA) to obtain porous hydrogel nanocomposite beads with higher lead removal and regeneration capability than any other chitosan hydrogel material or activated carbon. In the present study, we determine the effects of different concentrations of GO in the nanocomposite, as well as the role of pH and nanocomposite load in Pb2+ removal. The mechanisms of sorption and diffusion of lead in this new nanocomposite, as well as its reusability after regeneration were also investigated. The results show that the addition of GO into the polymer blend has increased significantly the metal uptake capacity owing to the additional oxygen-containing functional groups present in GO and the increase in surface area. Additionally, the solution pH affected the nanocomposite adsorption, with the best adsorption occurring at pH 5. The most economical adsorbent loading was determined to be 37.5 g of hydrogel beads per liter of solution. The pseudo second-order model best described the adsorption kinetics and determined that chemisorption was the mechanism of lead removal. The diffusion mechanism of this new nanocomposite was determined using the intraparticle diffusion model, which suggested that adsorption occurred in three distinct phases. The adsorption isotherms for the hydrogel beads all showed excellent fit to the Langmuir isotherm model. The CS–PAA beads with 5% GO presented the highest Pb2+ adsorption capacity (138.89 mg g−1). When this material was subjected to 3 cycles of adsorption–desorption, relatively high removal values were obtained, indicating good reusability and showing that the GO–CS–PAA nanocomposite beads could be applied to remove lead from water.

Enhanced ozonation of selected pharmaceutical compounds by sonolysis.

In search of new options to achieve removal of pharmaceuticals in the environment, combined ultrasound and ozonation has become a focus of intense investigation for wastewater treatment. In this study, three pharmaceuticals were selected as model compounds for degradation experiments: diclofenac (DCF), sulfamethoxazole (SMX) and carbamazepine (CBZ). Comparison of the degradation rates for both ozonation and combined ultrasound/ozonation treatments was performed on single synthetic solutions as well as on a mixture of the selected pharmaceuticals, under different experimental conditions. For single synthetic solutions, the efficiency removal for ozonation reached 73%, 51% and 59% after 40 min for DCF, SMX and CBZ, respectively. Comparable results were obtained for pharmaceuticals in mixture. However, the combined ultrasound/ozone treatment was found to increase degradation efficiencies for both DCF and SMX single solutions up to 94% and 61%, respectively, whereas lower removal yields, up to 56%, was noted for CBZ. Likewise, when the combined treatment was applied to the mixture, relatively low removal efficiencies was found for CBZ (44%) and 90% degradation yield was achieved for DCF.

Control of fouling formation in membrane ultrafiltration by ultrasound irradiation

The increasing application of membrane filtration in water and wastewater treatment necessitates techniques to improve performance, especially in fouling control. Ultrasound is one promising technology for this purpose as cavitational effects facilitate continuous cleaning of the membrane. This research studied the ultrafiltration of lake water in systems with constant permeate flux under medium frequency (45 kHz) ultrasound irradiation. Fouling was investigated by monitoring transmembrane pressure (TMP) using continuous or intermittent ultrasound irradiation and dead-end or crossflow operation. Best performance was observed with continuous ultrasound irradiation in crossflow mode. Intermittent irradiation reduced the rate of TMP build-up but nevertheless allowed irreversible fouling to develop.

Patchwork of land use, tapestry of risk

The links between built form and environmental health are, as yet, inadequately understood. Risk is a formless and ambiguous phenomenon tightly embedded in the myriad pattern of land uses that generate it. Our research, which is founded on a contextualist notion of policy design, demonstrates the potential of innovative land use policy instruments (i.e. form-based codes, conditional use permits) to address risk. We model environmental risks from point and mobile sources in Southeast Los Angeles (SELA), a known air toxics hotspot. We compare risk contours before and after implementation of land use interventions. The use of innovative form-based codes for modifying built environments results in appreciable risk reductions around transportation corridors in SELA. Conditional use permits employing technological standards for commercial and light-industrial land uses also produce some risk reductions. This research suggests an untapped potential for land use planning instruments to address the environmental health impacts of built form.

Material Recovery and Environmental Impact by Informal E-Waste Recycling Site in the Philippines

Waste electrical and electronic equipment (WEEE or e-waste) contains both valuable and hazardous substances and there is great demand for metal scrap. To better understand both material recovery and the environmental impacts by informal recycling of e-waste, and to find potential ways to improve the process, we carried out a field survey at an informal recycling site in the Philippines. We identified the Au recovery process used at the site and evaluated the layout of the recycling site. We collected 31 soil samples at the recycling site and analyzed the metal contents of each sample to clarify the metal distribution within the site. We determined that valuable substances (such as Au), as well as hazardous substances (such as Pb), were scattered throughout the soil at the informal recycling site. The results of our cluster analysis indicated that Au, Ag, Pb, and Sb were categorized in the same group. Improvements are needed in the metal recovery process and in hazardous substance emission control in the informal recycling.